Fetch List Using DTO projections using a Constructor Expression and JPQL

Question

Perform a search on DisabScreenRequest and fetch its child details also. Using DTO projections using a Constructor Expression and JPQL.

The parent entity with a child

Answer 1

If you need to fetch parent entity with a collection of its nested child entities you can use this simple approach using @EntityGraph annotation or JPQL with join fetch:

@Entity
public class Parent {
    //...
    @OneToMany
    private List children;
}

@Entity
public class Child {
    //...
}

interface ParentRepo extends JpaRepository {

    // with @EntityGraph
    @EntityGraph(attributePaths = "children")
    @Override
    List findAll(); 

    // or manually
    @Query("select distinct p from Parent p left join fetch p.children")
    List findWithQuery(); 
}

Note to use distinct in your query to avoid duplicate records.

Example: duplicate-parent-entities

More info: DATAJPA-1299